Re: What is the formula?
The nominal amounts don't really matter. What is important is the present value of the two streams of cash. Using a very conservative discount rate, I come up with the stream of payments starting now is worth a LOT more than the stream of payments if you start at age 65 (about $23k vs. $15k). If I were in your shoes, I would start payments now.
"Neither my companion or I carry firearms on our persons. We depend on the goodwill of our fellow man and the forbearance of reptiles."
- English Bob